Lapping, grinding, cutting, and polishing, collectively referred to herein as “lapping,” are key manufacturing technologies for shaping various ceramic and metallic materials. Lapping provides a mechanism to shape the surface of a substrate.
Lapping is often performed using a versatile, high-precision polishing machine using a scrolled cast iron plate. The machine generally includes a reciprocating roller bar mechanism to hold the sample in position while allowing for constant plate conditioning during the preparation process. In some applications, the lapping comprises a medium grit (10 to 15 micron) silicon carbide powder, suspended in a lapping composition. Other abrasive materials include medium grit aluminum oxide, boron carbide, and the like. By “lapping composition,” Applicant means a fluid used during a process to shape the surface of a substrate, where that process includes contacting a target surface of the substrate with one or more abrasives while also contacting that target surface with the lapping composition.
The choice of abrasive depends on the type of material—a very aggressive abrasive, such as diamond will cause a deeper damage layer at the surface. Damage penetration can be reduced by decreasing the load on the sample and the plate speed as the final thickness is approached.
After lapping, the sample can be polished using chemo-mechanical suspensions of, for example, colloidal silica (0.125 micron) or aluminum oxide (0.3 micron). The slurry suspensions comprising one or more abrasives suspended in Applicant's lapping composition are pumped continuously over the plate.